Github Desktop Protocol Handler Fix
A simple greasemonkey userscript that works around the bug that the beta GitHub Desktop client introduced. When one installs the beta client then switches back to using the stable Github Desktop client, "Open in Desktop" protocol handler links on the github.com website no longer work.
Userscripts for Windows and macOS (untested) are available.
Tested with TamperMonkey 4.3.6 for Chrome 59.0.3071.115 (Official Build) (64-bit) on Windows 10 Pro (64-bit) version 1607.